Natural selection is the mechanism of evolution that acts on the heritable variations of individuals and results in a population that is better adapted to its current environment. In the following sections, you will learn more about natural selection, adaptation, and the sources of genetic variation within populations.

Rainforest hummingbird populations offer a rich look into how the process of natural selection works. Watch Video for Students: "How Does Evolution Really Work?" to get an overview of natural selection. After watching, think about:

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What are the key components of natural selection?

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What kinds of limited resources can create a struggle between individuals in a population?

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What kinds of variable traits within a population might natural selection act upon?

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How does natural selection affect the genetic variation within the next generation of the same population?